There is a method of obtaining an oxide superconducting thin film by preparing a substrate and depositing an oxide superconductor on a substrate, which is a conventional technique for putting an oxide superconducting material to practical use.
For example, RE-based superconductors (RE: rare earth element), which exhibit a superconducting phenomenon at liquid nitrogen temperature (77 K) or higher, particularly yttrium-based superconductors (hereinafter referred to as “YBCO”) represented by a composition formula of YBa2Cu3O7−δ, are often used as the oxide superconductor to be deposited.
Oxide superconducting thin films using the RE-based superconductors are expected to be applied to superconducting fault current limiters, cables, and superconducting magnetic energy storages (SMES), and RE-based superconductors and manufacturing methods thereof have drawn a lot of attention.
However, obstacles to practicalization of oxide superconducting materials, including the RE-based superconductors (particularly, oxide superconducting thin films that is formed in the form of a thin film), include difficulty in improving the critical current density characteristics (hereinafter simply referred to as “Jc characteristics”).
For example, the practicalization of superconducting fault current limiters using oxide superconducting thin films requires that a largest possible electric current flow with a resistance of zero, which in turn requires that the Jc characteristics of the oxide superconducting thin films be improved.
Patent Document 1 (Japanese Patent Application Laid-Open (JP-A) No. 2005-290528) discloses a method of manufacturing an oxide superconducting thin film, in which a buffer layer (intermediate layer) formed of CeO2 or the like and a superconducting layer formed of an RE-based superconductor or the like are formed on a substrate obtained by cutting a sapphire single crystal at an angle several degrees different from the r-plane or a-plane thereof followed by grounding, whereby the Jc characteristics of the oxide superconducting thin film are improved.